Electric motor



0er (C A'TTORNEY F. M. NIERLICH May 8, 1934.

ELECTRIC MOTOR Filedpril 17. 1930 Patented- Mey 8, 1931 UNITED STATESPATEN'U OFFICE ELE'C'I'BIC MOTOR Fred M. Nlerllch, Stanford, Conn.,aulgnor to Electrlc Speclnlty Co. Stanford, Cum, a corpontlon o! Mypresent invention relates generally to electric motors, and ha.sparticular reterence to s. synchronous motor of the induction type.

Although I have herein illustrated and shall hereinafter describe myinvention as lt relates to a. motor, nevertheless it will be understoodthat a.s to certain phases of my inventlon it may be found applicable toelectric dynamo machines in general.

It is a general object 01 my invention to provide an improved type o!synchronous motor designed to operate at a substantially consta.nt speedand having improved starting und running characteristics, a relativelyhigh power factor, and of simple mechanical construction, resulting inincrease'd efflciency o1 manufacture und use.

It is a more particular object 01 my invention to provide an improvedmachine capable 01 exerting a relatively great starting torque with arela- 2o tively small drainage 01 starting current.

A general l'eature o! the lnvention lies in utilizing the advantageouscharacteristics 01 the commutator or repulsion-type motor, incombinatio'n with those 01 the well-known squirrel-cage type 5 ofinduction motor to attain the practical advantages of both said types 01motors, und to minimize the disadvantage 01 each. Synchronizing recessesund openings are preferably provided more adequately to assuresynchronlsm.

In accordance with my present invention, I have provided a simplifieddynamo electric machine which operates with high efliciency, which hasa. high power factor, a streng starting torque, a strong pull-in torque,and which utllizes less starting current and less running current thanpx=i0r squirrel-cage split-phase and polyphase salient-pole synchronousmotors.

The improved motor which my invention provides may be manufacturedinexpensively and may be built to operate on either single-phase orpolyphase current 015 any desired commercial voltage or frequency.

For the attainment of the foregoing objects and such other objects asmay hereinatter appear or be pointed out, I have constructed a deviceembodying the features of my invention and illustrated in theaccompanying drawing, wherein:

Fig. 1 is a fronb view of a rotor laminatlon embodying the features o1my present invention; und.

Fig. 2 is a front view of a motor, partly}n section, showing therelationships 01 the severa.l windings and structural characteristics.

In the embodiment herein chosen for illustration, I have shown a motorconstruction having an annular stator of the type conventionallyemp1oyed in motors 01 the repulslon and inductlon type. For example, inFig. 2, it will be noted that the stator 10 is provlded with the slots11 arranged on its interlor face, these slots being adapted to receivewindings 12 which a.re suita.bly connected 50 in the usual manner to anexternal source 01 supply current. The particular structure shown 1ssubstantially like the structure of the usual repulsion or 01 the usualinduction motor.

The novel characteristics of my present invention will be more fullyappreciated upon reference 130 Fig. 1, in which I have shown one 013 theInminations of which the rotor is constructed. The disc 13 issubstantially circular in configuration as is customary, a.nd isprovided with the central, axial opening 14 adapted to receive -the hubor shaft 01 the motor. The periphery is provided with radial slots 15which extend completely around the disc. At circumferentially-spacedintervals the length of certain 015 the teeth or projections is reducedwhich deflne the slots 15, thereby producing a series of marginalrecesses 16. Four 015 these recesses are shown by way o! example in theillustrated embodiment but a. lesser or greater number of these slotsmay be used to advantage. Each recess is shown of width at least asgreat a.s two of the slots 15 although the invention is not: limited tomaking the recess of said width. When the roter laminations a.reassembled, in the usual manner, the recesses 16 35 register withcorresponding recesses in other laminations a.nd provide a composite,axial recess arranged in the outer surface er periphery 015 the rotorstructure.

The slots 15 are adapted to receiving windings, and in accordance withmy present invention, these windings are of the usual repulsion-motortype. In Fig. 2, these windings are designated by the reference numeral17.

Arranged around the central opening 14 01 the disc 13 are a series 01relatively large holes or openings 18 adapted to register with similaropenings in the remaining laminations 015 the structure to provide aset; of openings or holes extending longitudinally through the eure ofthe roter. In the illustrated embodiment, Iour of these openings 18 areshown equally spaced in a circumferential manner, and staggered withrelationship to the recesses 16 previously referred to. The marginalrecesses 16 and the axial openings 18 serve as synchronizing recessesund. openings by guiding the magnetic flux through the desired paths. v

In a. preferred construction herein illustrated, the roter also carriesa squirrel-cage winding;

and to accommodate the copper bars 01 such a cage, a sei; ofcircumferentially-arranged holes 19 is provided in each disc 13, theholes 19 being relatively small as compared with the holes 18 and beingarranged radially inside oif the slots 15.

Tims, when the rotor structure has been assembled, and the severalwindings applied thereto a cooperative association is provided betweenthe repulsion-motor winding, the squirrel-cage winding, and thesynchronizing recesses und holes.

When the motor is started, a very streng torque is exerized by virtueoi' the repulsion-motor windings l'l. The synchronizing recesses 16prevent the roter irom rur'ming too fast o1 too slow with respect to thesynchronous speed 01 the machine, but inasmuch as the synchronizingeflfect cf these recesses alone may not be sufllcieni: 1:0 carry a loadcommensurate with the size oi' the machine, I adjust the brushes so thatthe repulsion-winding contributes a strong toxque and tends toaccelerai:e the rotor above synchronous speed. Accordingly, at lightloads, the roter will tend to lead with respect to the amplitude of thesteter flux; bui: as the load increases the roter changes the relativephase angle with respect to the amplitude 01 the flux, and under heavyoverload couditions the roter tends to lag and to drop oui; ofsynchronism.

The Ioregoing action 015 the repulsion-winding, with properly setbrushes, not only contributes greatly to an increase of the rotertorque, bui: serves to improve the power factor and eiliciency 0f themotor to a degree heretofore unattained by synchronous motors, withoutdirect current excitation.

The cage-winding has a stabilizing efiect under heavy loads, tending tomaintaip the rotor ai: synchronous speed and counteracting its tendencyto lag. Accordingly, the cage-winding serves to increase the torquewhich the roter delivers at synchronous speed.

It will thus be seen thai; I have provided a motor of greatly improvedcharacteristics a.ncl o! simple, inexpensive, yet staunch construction.N0 auxiliary apparatus is requirecl i'or starting; no direct currentexcitation is needed; und yet, the starting torque is greater while thestarting current is reduced to about one-third. Frthennore, the powerfactor is practically doubled; the running current is reduced by aboutflfty per oent; and the general efllciency oi' the motor is increased byat least twenty per cent.

Although I have shown separate openings in the roter to accommodate thecage-winding, where such winding is employed, it will be understood thati:his winding may, i! desired, be laid in the slots thai: accommodatethe repulsion-motor winding.

It will thus be seen that there is herein described apparatus in whichthe several features o! this invention are embodied, und which apparatusin its action attains the varioi1s objects of the invention and is wellsuited to meet the requirements oi practical use.

As many changes could be made in the above construction, and manyapparently widely difl'erent embodiments of this invention could be madewithout departing from the scope thereof. it is intended that all mattercontained in the above description or shown in the accompanying drawingshall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention and illustrated its use. what I claimas new and desire to secure by Letters Patent is:

1. In a synchfonom motor. a roior comprlaing a laminated structureprovided with a set ot circum1exentially-spaced longitudinalsynchronizing recesses in its outer suriace, and a set oi'repuiaionmotor windings carried by said roter at said suriace. the roterhaving slots therein i:o rooeive said windings, some ot said slots lyingat the bottom o! said recesses.

2. In a synchronous motor, a roior comprising a laminated structureprovided with a sei; oi circumi'erentially spaced longitudinalsynchronizing recesses in its outer suriace, a squirrel cagewindingcarried by said roter, and disposed cioser to the axis 01 said rotorthan are said recesses, and windings carried by the rotor, some 01 whichlie between the squirrel cage-winding and the recesses.

3. In a synchronous motor, a roter comprising a laminated structureprovided with a set 01 circumIerentially-spaced longitudinalsynchronizing recesses in its outer suri'ace, a set o! repulsionmotorwindings carried by said roter, some 01 said windings being at thebottom 01 said recesses, and a squirrel cage-winding carried by saidroter beneath the flrst named windings.

4. In a synchronous motor, a roter comprising a laminated structureprovided with a set 01 circumierentially spaced longitudinalsynchronizing recesses in ii:s outer surtace, said structure beingprovided also with a serles of synchronizing holes 106 extendinglongitudinally therethrough, and a set 01 repulsion-motor windingscarried peripherally by said rotor structure.

5. In a synchronous motor, a roter comprising a laminated structureprovided with a set 01 cir- 110 cumierentially-spaced longitudinalsynchronizing recesses in its outer surtace, said structure beingprovided also with a separate series oi! open synchronizing holesextending axially therethrough, windings at the bottom 01 said recessesand a squirrel cage-winding carried by said structure.

6. In a synchronous motor, a roter comprising a. laminated structureprovided with a set 01 circumterentially-spaoed longitudinalsynchronizing holes extending through the core thereoi', and a set o!repulsion-zzotor windings und also a squirrel cage-winding carried bysaid structure between said holes and said repulsion motor windinss.

7. In a synchronous motor, a roter comprising a laminated structureprovided with a set oi circumi'erentially-spaced longitudinalsynchronizing recesses in its outer surlace, said structure beingprovided also with a series 01 synchronizing holes extending axiallytherethrough, a repulsion-motor winding carried peripherally by saidrotor structure, a.nd a squirrel-cage winding beneath said flrst-namedwinding.

8. A synchronous mutet comprising an annular stator, a set o! windingscarried along the Interim surface thereof, a rotor having a slottedperiphery, a set o! repulsion-xnotor windings in said slots. und asquirrel cage-winding carried by said roter beneath said repulsion-motorwindings; said roter being provided with a set 01 longitudinalsynchronizing recesses in its peripheral surface, and with a set o!synchronizing holes extending longitudinally through the core thereof.

9. A synchronous motor comprising an annular stator, a set 01 windingscarried along the interior suri'ace thereot, a roter having a slottedperiphery, a set of repulsion-motor windings in said slots, and asquirrel cage-winding carried by said rotor beneath said repulsion-motorwindings; said rotor being provided with a set 01 longicentral opening,and windings at the bottom of said recesses.

11. A roter lamination comprising a, substantia.lly circular disc witha. slotted periphery, said disc being provided with a. set 01 marginalrecesses arranged ab spaced interva.ls said disc being provided with aset 015 circumferentially-arranged holes lying radially inwardly o! saidslots, and sa.id disc being also provided with a series 01 relativelylarge holes circumferentially ananged relatively close to the center o!the disc.

FRED M. NIERLICI-I.

